Insight into the electron transfer regime of periodate activation on MnO2: The critical role of surface Mn(IV)

• Published in: Journal of hazardous materials Vol. 454; p. 131479
• Main Authors: Yang, Liwei, Yang, Fashan, Zhang, Heng, Zhou, Hongyu, Luo, Mengfan, Liu, Yunmei, Zhao, Chuanliang, Zheng, Lu, Lai, Bo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.07.2023
• Subjects: Crystal forms; Electron transfer; MnO2; Periodate; Surface Mn(IV) content; MnO2; Electron transfer; Surface Mn(IV) content; Crystal forms; Periodate
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.131479

At present, the potential mechanism of manganese oxide (MnO2) activation of PI and the key active sites of PI activation are still unclear and controversial. To this end, three different crystal forms of MnO2 were prepared in this study and used to activate PI to degrade pollutants. The results showed that different crystal types of MnO2 showed different catalytic abilities, and the order was γ-MnO2 > α-MnO2 > β-MnO2. Through quenching experiments, EPR tests, Raman experiments and in situ electrochemical experiments, it has been confirmed that electron transfer-mediated non-free radical process is the main mechanism of pollutant degradation, in which the active substance is the highly active metastable intermediate complex (MnO2/PI*). Hydroxyl radical (HO•), superoxide radical (O2•−), singlet oxygen (1O2) and iodine radical (IO3•) did not participate in pollutant degradation. The quantitative structure-activity relationship analysis confirmed that the catalytic performance of MnO2 was highly positively correlated with the surface Mn(IV) content, which indicated that the surface Mn(IV) site was the main active site. Overall, this study will be of great help to the design and application of manganese dioxide activation for periodate degradation of pollutants. [Display omitted] •α-MnO2, β-MnO2 and γ-MnO2 could all effectively activate PI.•The α-MnO2/PI, β-MnO2/PI and γ-MnO2/PI systems were non-radical processes dominated by electron transfer.•The high activity of metastable intermediate complex (MnO2/PI*) was the main factor for organic pollutants removal.•The catalytic activities of MnO2 were positively correlated with the content of Mn (IV) on the catalyst surface.